Field of the Invention
The present invention relates to a toner for use in electrophotographic systems, electrostatic recording systems, electrostatic printing systems and toner jet systems.
Description of the Related Art
As electrophotographic full-color copiers have become popular in recent years, there has been increasing demand for higher printing speeds and energy savings. To achieve higher printing speeds, techniques are being investigated for melting the toner more rapidly during the fixing process. Further, to save energy, techniques are being investigated for fixing the toner at lower fixation temperatures so as to reduce power consumption during the fixing process.
Methods for improving the low-temperature fixability of the toner that are compatible with high-speed printing include lowering the glass transition point or softening point of the binder resin in the toner, and using a binder resin with a sharp melt property. In recent years, toners containing crystalline polyester resin in the binder resin have been developed as a way of further improving the sharp melt property. Because a toner containing a crystalline polyester melts rapidly at the fixation temperature but maintains its hardness at temperatures up to the fixation temperature, it can have improved storage stability and durability.
In the case of toners containing crystalline polyester, various techniques relating to the state of the crystalline polyester in the toner have been proposed.
In the technique disclosed in Japanese Patent Application Laid-open No. 2011-145587, the area of the domains of the crystalline polyester in the toner is 0.2 to 0.8 times the area of the domains of the wax in a cross-section of a toner containing a crystalline polyester and a wax. It has been shown that with this technique, toner breakage is reduced and the resulting toner is very durable. Moreover, the speed at which the wax seeps to the surface of the toner is optimally balanced with the melting speed of the toner binder resin, resulting in both low-temperature fixability and good fixing separability.
In Japanese Patent Application Laid-open No. 2012-63559, a crystalline polyester dispersing agent is used in addition to the principal binder resin and crystalline polyester, and the solubility parameters of each are defined. The object here is to reduce exposure of the crystalline polyester on the surface layer of the toner, and finely disperse the crystalline polyester inside the toner particles, thereby suppressing toner filming on other members and improving hot offset resistance.
Japanese Patent Application Laid-open No. 2012-18391 proposes a toner containing a finely dispersed crystalline resin, with an amorphous resin coated on the surface layer of the toner particles. Heat-resistant storability, durability and stability are thus achieved in a toner with excellent low-temperature fixability containing a crystalline polyester.
Japanese Patent Application Laid-open No. 2004-279476 proposes improving hot offset resistance by giving the crystals of the crystalline polyester in the toner a major axis diameter of at least 0.5 μm and no more than ½ the diameter of the toner.